Background Diagnosing sepsis in critical care remains a challenge due to the lack of gold-standard diagnostics. Calprotectin (S100A8/A9) has been proposed as a diagnostic marker to identify sepsis in critically ill patients. This study evaluated the diagnostic performance of calprotectin and C-reactive protein (CRP) to distinguish between sepsis and non-sepsis on intensive care unit (ICU) admission. Methods Admission biobank blood samples from adult patients admitted to four ICUs (2015-2018) were used to analyse calprotectin and CRP. All adult patients were screened retrospectively for the sepsis-3 criteria at ICU admission. The diagnostic performance of calprotectin and CRP was evaluated using receiver operating characteristic (ROC) curves. Results We included 4732 patients, of whom 44% had sepsis. Calprotectin levels were higher in sepsis (p<0.001). The area under the receiver operating curve (AUROC) to diagnose sepsis was 0.61 for calprotectin compared to 0.72 for CRP (p<0.001). Among microbiological subgroups of sepsis patients, fungal sepsis had the highest level of calprotectin. Conclusions The diagnostic performance of calprotectin in identifying sepsis patients at ICU admission was inferior to that of CRP.

The authors have declared no competing interest.

Lund University provided Open Access funding. ML: regional research support, Region Skaane #2024-2023-2142 and #2022-2021-1069. HK: Kristianstad Hospital, Department of Anaesthesia and Intensive Care. LM: Governmental funding of clinical research within the Swedish National Health Service (ALF). HF: Regional research support, Region Skaane; Governmental funding (ALF); Skaane University Hospital grants; Hans-Gabriel and Alice Trolle-Wachtmeisters Foundation for Medical Research. AS: the Swedish Heart and Lung Foundation; The Swedish Research Council; The Ministry of Research, Innovation and Digitalization of Romania (project number PNRR-C9/I8-CF148). AF: Regional research support, Region Skaane #2022-1284; Governmental funding of clinical research within the Swedish National Health Service (ALF) #2022:YF0009 and #2022-0075; Crafoord Foundation grant number #2021-0833; Lions Skaane research grants; Skaane University Hospital grants; Swedish Heart and Lung Foundation (HLF) #2022-0352 and #2022-0458. The funding organisations had no role in the design and execution of the study (collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and the decision to submit the manuscript for publication).

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Ethics committee of Lund University gave ethical approval for this work

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